Variable temperature refrigeration



{959 c. s. HERRxcK VARIABLE TEMPERATURE REFRIGERATION Filed Sept. 30,1954 VARABLE TEMPERATURE REFRHG-ERATION Car'iyia S.. Herrick, lplaus, N.Y., assigner to General Electric Company, a corporation of New YorkApplication September 38, 1954, Serial No. 459,442

3 Ciainis. (Cl. 62-174) This invention relates to refrigeration systemsand specifically t-o a method and apparatus to secure variabletemperature levels in such systems.

A refrigeration system, which is capable of providing variabletemperature levels, is desirable in heat pump construction and incommercial and domestic refrigerators. It is desirable that a reverserefrigeration system or heat pump employ a selectively variablerefrigerant mixture to match capacity with load over a wide variation inthe evaporator temperatures. A single refrigerant system will not matchcapacity with load unless the load is constant.

Accordingly', it is an object of my invention to provide a new andimproved refrigeration system in which a pair of low temperatureimmiscible refrigerants with different volatility and densitycharacteristics are employed.

it is another object of the invention to provide a refrigeration systemwhich selectively circulates a refrigerant mixture of variablecomposition in response to the load upon the system.

it is another object of the invention to provide a refrigeration systemin which a pair of liquid receivers are employed.

It is a further object of the invention to provide a novel method ofrefrigeration in which a pair of low temperature immiscible refrigerantsare separated and selectively mixed in the refrigeration system toproduce variable temperature levels of refrigeration.

In carrying out my invention in one form, a pair of low temperatureimmiscible refrigerants are selectively mixed and circulated in arefrigeration system to provide variable temperature levels ofrefrigeration.

These and various other objects, features and advantages of theinvention will be better understood from the following description takenin connection with the accompanying drawing in which:

Fig. l is a schematic view of one form of a refrigeration systern whichembodies my invention; and

Fig. 2 is a solubility graph determined -at the system pressure of aperfluoropropane (C3118) and Freon 3l (CHgClF) solution in whichcomposition in weight percentage is plotted against the temperature indegrees Fahrenheit.

In Fig. l of the drawing, a refrigeration system, which may be used inheat pump construction or in commercial or domestic refrigerators andwhich is indicated generally at 1Q, comprises a compressor 11 whichcommunicates on its high pressure side with a condenser 12. Condenser 12is connected to a liquid running receiver 13 in which a pair of lowtemperature immi'scible refrigerants 14 and 15 coexist in a mixture 16to form one liquid phase of desired composition. A liquid storagereceiver 17 is filled completely with additional amounts of essentiallypure refrigerants 14 and 15 in two separate liquid phases immiscible onewith the other. A tube 18 connects receiver 13 to receiver 1'7 tomaintain condenser pressure in receiver 17 and to replenish refrigerants14 and 15 from refrigerant mixture 16 in receiver 13. The main- ECCtenance of receivers 13 and 17 at condenser pressureeliminates a liquidlevel control therebetween.

Refrigerant mixture 16 is circulated from receiver 13 through a tube 19to a heat exchange coil 20 Whichlispositioned within receiver 17. A tube21 connects coil 20 to an evaporator 22 which communicates with the lowpressure side of compressor 11. Coil 20 carries mixture 16 expanded to alow temperature to cool immiscible refrigerants 1-1 and 15 in receiver17 to approximately the evaporator temperature of the refrigerationsystem. An expansion valve 23 of a conventional type which is operated'by a pressure tube 24 and diaphragm 25 is positioned in tube 19. Atemperature-operated or thermostatic valve or sections of capillarytubing may be employed as the expansion device.

A three-way, three-position valve 26 controls a pair of outlets 27 and Zwhich communicate with refrigerants fili and 15 in receiver 17. A loadsensing and sequence control device 2.9 of any conventional constructionis provided to selectively operate valve 26 in response to the systemload. A tube Si) connects valve 26 to tube 19 between receiver 13 andexpansion valve 23. lf it is desired, tube 30 may be connected to tube19 at the low pressure side of valve 23.

Low temperature immiscible refrigerants 1d and 15, which have differentvolatility and density characteristics are selectively mixed andcirculated through the refrigeration system in response to the loadthereon. It is important that each of the refrigerants which is selectedfor Acirculation in the system has a different density from the otherrefrigerant and exhibits insolubility in the other refrigerant of thepair at or below customary evaporator temperatures to provide aseparation of the refrigerants into two layers in storage receiver 17.The following pairs of refrigerants, which exhibit differentvolatilities, solubilities and densities and which possess immiscibilityat customary evaporator temperatures, are given as examples of suitablerefrigerant combinations to be employed in a variable temperaturesystem: peruoropropane (C3138) and methyl chloride (CHBCl),perfluoropropane (C3133) and Freon 3l (CligClF), perfluorobutane (CFw)and Freon 2l (CHCIZF), peruorobutane (C4F10) and methyl chloride(CHgCl), Freon 115 (C2F5Cl) and sulfur dioxide (SO2), peruoropropane(CSFB) and methyl bromide (CHEBr), Freon (C2F5Cl) and methylene chloride(CH2C12), perfluorobutane (C4F10) and methylene chloride (CHzClz), andperiluorobutane (C4Fw) and ethyl chloride (C2H5Cl).

in the operation of the refrigeration system in Fig. l, the pair ofrefrigerants 14 and 15, which form a refrigerant mixture 16 in liquidrunning receiver 13, are selectively mixed and circulated in the system.Three-way, three-position valve 26 is shown in open position for outlet27 and tubelil and in closed position orvoutlet 28. Compressor 11 pumpsrefrigerant mixture .16 through condenser 12 to liquid running receiver13. Refrigerant mixture 16 is then-circulated through tube 19, expansionvalve 23, coil 21B, tube 21, and evaporator 22 to the inlet side ofcompressor 11. When outlet 27 is opened to tube 30, refrigerant 14 isadded to refrigerant mixture 16 which is circulating in the system. Anequal volumeiof refrigerant mixture 16 is simultaneously conveyed fromreceiver 13 to receiver 17 through tube 18. While complete liquidmiscibility may exist at liquid running receiver temperatures, i. e., 65F. or higher, essentially complete immiscibility exists at temperaturesequal to or less than evaporator temperatures. Coil 2li in receiver 17maintains the temperature therein at evaporator temperature to separaterefrigerant mixture 16 into refrigerants 1li and 15 in two immisciblephases.

When the load on the system changes, it activates load sensing andsequence control device 29 to close out- 2,867,094 Patented Jan. 6, 1959let 27 and to open outlet 28 whereby refrigerant 15 is added torefrigerant mixture 16 in the same manner as refrigerant 14. Thecomposition of refrigerant mixture 16 is determined by the system loadthrough a load sensing and sequence control device 29 which operatesvalve 26 to admit additional essentially pure refrigerant 14 or to thesystem. It should be noted, however, that at relatively hightemperatures refrigerants 14 and 15 in the storage receiver 17 may bepartly in solution with each other such that, in the preliminaryoperation of this system, either of the refrigerants from storagereceiver 17 that may be added to the system would not be insubstantially pure form. As the temperature in the evaporator isreduced, the temperature in the storage receiver is also reduced throughthe action of the refrigerant expanding through coil 20 in storagereceiver 17. Therefore, refrigerants 14 and 15 progressionally separateuntil they are in substantially pure form. Thereafter, capacitymodulation may be attained for high or low capacity by circulatingeither refrigerant 14 or 15 in their substantially pure form through thesystem. The volume of refrigerant mixture 16 remains constant throughthe simultaneous addition to and withdrawal from the circulatingrefrigerant mixture. The refrigeration system circulates eitheressentially pure refrigerant 14 or 15 or a refrigerant mixture 16 of anydesired composition.

In Fig. 2, a solubility graph is shown in which composition in weightpercentage of a peruoropropane (C3138) and Freon 3l (Cl-12CH?) mixtureis plotted against the temperature in degrees Fahrenheit. Such arefrigerant mixture is generally miscible above about 45 F. andimmiscible below this temperature. The temperature of storage receiver17 in Fig. l is maintained at or below evaporator temperature tomaintain refrigerants 14 and 15 in two immiscible phases. If thetemperature of the refrigerants in the receiver 17 is assumed to be 20F. for purposes of illustration, one immiscible refrigerant phase iscomposed of about 86% by weight of perfluoropropane (C3128) and about14% by weight of Freon 3l (CHZClF). The other refrigerant phase is about84% Freon 3l and about 16% peruoropropane.

As will be apparent to those skilled in the art, the objects of myinvention are attained by the use of a pair of immiscible refrigerantswith diterent characteristics which are separated and then selectivelymixed and circulated in a refrigeration system to provide variabletemperature levels of refrigeration and refrigeration capacities.

While other modifications of this invention and variations of apparatuswhich may be employed in the scope of the invention have not beendescribed, the invention is intended to include all such as may beembraced within the following claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A refrigeration system comprising a compressor, a condenser connectedin uid ow relation to said cornpressor, a liquid receiver maintained atcondenser pressure and connected in fluid flow relation to saidcondenser, a supply of low temperature immiscible refrigerants in saidreceiver, an evaporator, a conduit connecting said receiver to saidevaporator, means connecting said evaporator to said compressor in uidow relation, a storage receiver maintained at condenser pressure, asupply of low temperature immiscible refrigerants in two separate liquidlayers within said storage receiver, said storage receiver arranged toreceive refrigerant from said liquid receiver, said conduit connectingsaid liquid receiver to said evaporator being positioned partiallywithin said storage receiver in heat exchange relationship to therefrigerants therein, and means to selectively add one of therefrigerants fromthe storage receiver to the system.

2. A refrigeration system comprising a compressor, a condenser connectedin uid ilow relation to said compressor, a liquid receiver maintained atcondenser pressure and connected in fluid ilow relation to saidcondenser, a supply of low temperature immiscible refrigerantsin saidreceiver, an evaporator, a conduit connecting said receiver to saidevaporator, means connecting said evaporator to said compressor in uidflow relation, a storage receiver maintained at condenser pressure, asupply of low temperature immiscible refrigerants in two separate liquidlayers within said storage receiver, said storage receiver connected influid ow relation to said liquid receiver, said conduit connecting saidliquid receiver to said evaporator being positioned partially withinsaid storage receiver in heat exchange relationship to the refrigerantstherein, control means connected to each layer of refrigerant in saidstorage receiver and responsive to the load upon the system toselectively add a refrigerant from the said storage receiver tocirculate through the system, and means to expand the circulatingrefrigerant in the said conduit partially positioned within said storagereceiver to reduce the temperature of the refrigerants therein.

3. A refrigeration system comprising a compressor, a

' condenser connected in uid ow relation to said compressor, a liquidreceiver maintained at condenser pressure and connected in fluid iiowrelation to said condenser, a supply of low temperature immisciblerefrigerants in said receiver, an evaporator, a conduit connecting saidreceiver to said evaporator, means connecting said evaporator to saidcompressor in uid ow relation, a storage receiver maintained atcondenser pressure, a supply of low temperature immiscible refrigerantsin two separate liquid layers within said storage receiver, said storagereceiver connected in fluid flow relation to said liquid receiver, saidconduit connecting said liquid receiver to said evaporator havingv aheat exchange coil portion, said coil being positioned within saidstorage receiver, means for circulating the refrigerant in the runningreceiver through said system, means for expanding the refrigerantcirculating through said system through the said coil positioned in saidstorage receiver to vary the solubility of the refrigerants therein, andmeans to selectively add one of the refrigerants in said storagereceiver to the refrigerant circulating in the system.

References Cited in the file of this patent UNITED STATES PATENTS1,735,995 Davenport Nov. 19, 1929 2,255,585 Hubacker Sept. 9, 19412,277,138 Newton Mar. 24, 1942 2,483,842 Philipp Oct. 4, 1949 2,682,756Clark et al. July 6, 1954

